System and method for tracking inventory

ABSTRACT

An RFID enabled paper roll includes a tubular core, a paper stock wound around the core, and a radio frequency integrated circuit electrically coupled to an antenna and positioned on the core. A system for reading a radio frequency integrated circuit positioned on an item of inventory in a warehouse comprises a material handling device and an RFID reader coupled to the material handling device. The material handling device has at least member for use in transporting an item of inventory. The reader is configured to read the radio frequency integrated circuit associated with the item of inventory when the item is in proximity to the material handling device.

FIELD OF THE INVENTION

The claimed invention relates to wireless communication systems. Inparticular, the invention relates to a paper roll that incorporates RFIDcomponents and a system for tracking inventory having RFID components ina warehouse environment.

BACKGROUND

Radio frequency identification (“RFID”) technology has been used forwireless (i.e., non-contact, non-line of sight) automaticidentification. An RFID system typically includes an RFID transponder,which is sometimes referred to as an inlet or tag, and an RFID reader.The transponder typically includes a radio frequency integrated circuit(“RFIC”) and an antenna. Both the antenna and the RFIC can be positionedon a substrate. As used herein, the term “inlet” refers to an RFIC thatis coupled to a tag. The tag includes the antenna and may also include asubstrate on which the antenna is positioned.

The RFID reader utilizes an antenna and a transceiver, which includes atransmitter, a receiver, and a decoder incorporating hardware andsoftware components. Readers can be fixed, tethered, or handhelddevices, depending on the particular application. When a transponderpasses through the read zone of a reader, the transponder is activatedby the electromagnetic field from the reader antenna. The transceiverdecodes the data sent back from the transponder and this decodedinformation is forwarded to a host computer for processing. Datatransfer between the transponder and transceiver is wireless.

RFID systems may utilize passive, semi-passive, or active transponders.Each type of transponder may be read only or read/write capable. Passivetransponders obtain operating power from the radio frequency signal ofthe reader that interrogates the transponder. Semi-passive and activetransponders are powered by a battery, which generally results in agreater read range. Semi-passive transponders may operate on a timer andperiodically transmit information to the reader. Active transponders cancontrol their output, which allows them to activate or deactivateapparatus remotely. Active transponders can also initiate communication,whereas passive and semi-passive transponders are activated only whenthey are read by another device first. Multiple transponders may belocated in a radio frequency field and read individually orsimultaneously.

Inventory tracking in the paper industry is currently accomplished bypositioning optically readable bar codes on paper rolls that are storedin warehouses. Specialty paper rolls are often produced in quantitiesgreater than the current need and then excess quantities are stored inwarehouses for later use. Paper rolls can be six feet tall by eight feetwide and are conventionally wrapped in a protective paper wrapper. Rollsmay be stacked in a warehouse in rows that are, for example, 3 rollshigh.

Optically readable bar codes are positioned on the exterior of the paperwrappers of the rolls. Over time, the rolls can be moved or shuffledaround the warehouse. As a result, paper wrappers can be torn and thebar codes destroyed. Even where bar codes remain intact, when rolls aremoved, bar codes can oftentimes become unobservable because hidden fromview. As a result, paper rolls in inventory become lost in the warehouseand need to be reproduced when the customer places another order for theproduct. This results in great expense to the paper manufacturer. Inaddition, unidentifiable paper rolls remain in the warehouse taking upspace and are often neither used nor destroyed. These unidentifiablerolls continue to reside in the warehouse indefinitely, taking upvaluable space. A system that remedies these deficiencies is desirable.

SUMMARY

According to the claimed invention, an RFID enabled paper roll comprisesa core, a paper stock wound around the core, and a radio frequencyintegrated circuit (“RFIC”) coupled to an antenna and positioned on thecore. In a preferred embodiment, the core of the paper roll is tubularand the RFIC is positioned on an RFID inlet. The RFID inlet includes anadhesive surface and the adhesive surface is positioned on one of theinner or the outer surface of the core. The RFID inlet may include a taghaving a substrate, with the RFIC and antenna being positioned on thesubstrate.

The claimed invention also relates to a system for reading an RFIC orRFID inlet positioned on an item of inventory in a warehouse. The systemcomprises a material handling device and at least one RFID readercoupled to the material handling device. The material handling devicehas at least one member for use in transporting an item of inventory.The item of inventory has an RFIC associated therewith. The at least onereader is for reading an RFIC associated with the item of inventory whenthe item is in proximity to the material handling device.

In one embodiment of the system, the material handling device is a forklift truck and the at least one member is a pair of arms extendingoutwardly from the fork lift truck. The at least one reader ispositioned on the fork lift truck so that when the pair of arms are inproximity to the item of inventory, the at least one reader cancommunicate with the RFIC associated with the item of inventory. TheRFIC may be positioned on an inlet and be electrically coupled to anantenna, with the inlet being positioned on the item of inventory.

In another embodiment of the system, the system further comprises acomputer processor and a position locating system. The computerprocessor is in communication with the at least one reader for receivinginformation from the reader and transmitting information to the reader.The position locating system is for transmitting information to the atleast one reader and the computer processor. In a preferred embodiment,the position locating system comprises a plurality of RFID transmittersand at least one RFID receiver, with the RFID receiver being positionedon the fork lift truck and the RFID transmitters being positioned atspaced locations throughout the warehouse.

The claimed invention further relates to a method of tracking an item ofinventory in a warehouse. The method comprises providing the systemdescribed above, associating the pair of arms of the fork lift truckwith the item of inventory, and powering the reader on the fork lifttruck to communicate with the RFIC on the item of inventory to at leastone of read the information stored in the RFIC and write information tothe RFIC. The method may also include determining a preferred positionfor the item of inventory in the warehouse, transporting the item ofinventory to the preferred position, depositing the item of inventory atthe preferred position, determining the position of the item ofinventory once the item has been deposited, and storing the depositedposition of the item in at least one of the RFIC and the computerprocessor.

BRIEF DESCRIPTION OF THE DRAWING FIGURES

FIG. 1 is a cut-away perspective view of a paper roll showing aradio-frequency integrated circuit (“RFIC”) and an antenna positioned onthe core of the paper roll according to one aspect of the inventionwhere the antenna and RFIC are electrically coupled;

FIG. 2 is a cut-away perspective view of a paper roll showing analternative embodiment of an RFIC and an antenna positioned on the corewhere the antenna and RFIC are magnetically coupled;

FIG. 3 is a cross-sectional view of the paper roll of FIG. 1 taken atline 3—3, showing the antenna positioned on an exterior surface of thecore;

FIG. 4 is a cross-sectional view of a paper roll similar to that of FIG.3, but showing the antenna positioned on an inner surface of the core;

FIG. 5 is a schematic of a fork lift truck having clamp arms forengaging a roll of paper according to another aspect of the invention;

FIG. 6 is a front plan view of a fork lift truck and clamp armsincorporating antennae and RFID readers attached to the fork lift truck;

FIG. 7 is a front plan view of a fork lift truck and clamp armsincorporating different antennae and RFID readers attached to the forklift truck;

FIG. 8 is a front plan view of a fork lift truck and clamp armsincorporating an antenna and an RFID reader positioned around the liftmast of the fork lift truck;

FIG. 9 is a front plan view of a fork lift truck and clamp armsincorporating an antenna embedded in each of the clamp arms, with theRFID readers positioned on the clamp arms;

FIG. 10 is a schematic top view of a warehouse having a plurality ofRFID transmitters for communicating to several fork lift trucks at thesame time in the warehouse;

FIG. 11 is a schematic of a fork lift truck in a warehouse incommunication with the RFID transmitters; and

FIG. 12 is a schematic top view of an alternative embodiment of awarehouse having a plurality of RFID inlets installed in a grid patternin the floor of the warehouse.

DETAILED DESCRIPTION

One aspect of the invention relates to a paper roll 10 that incorporatesRFID components. The RFID components are for use in identifying thecontents and history of the paper roll 10, as well as its location orposition within a warehouse. In particular, FIGS. 1–4 show a paper roll10 having an RFID inlet 26 installed on the core 14 of the paper roll10. Another aspect of the invention relates to a system for reading RFIDcomponents installed on items of inventory 16, such as rolls of paper.The system, as shown in FIGS. 5–12, incorporates a material handlingdevice in the form of a fork lift truck 18 having an RFID reader 20 anda reader antenna 60 installed on the fork lift truck 18. Another aspectof the invention relates to a method of tracking inventory 16 in awarehouse 12 using the system. Each of these aspects will be discussedin greater detail below.

Inventory 16 in a warehouse 12 is typically stacked in multiple rows andcolumns, several rows deep and high. Inventory may include boxes orcases of products, among other types of inventory known to those ofskill in the art. One type of inventory for which the invention isparticularly useful is rolls of paper. Rolls of paper in a warehouseenvironment may be stored up to approximately 13 rolls deep and 3 rollshigh. A typical roll of paper ranges in diameter from about 2 to 8 feet,is approximately 6 to 8 feet tall, and weighs approximately 1 ton.

As shown in FIGS. 1–4, a roll of paper 10 includes a core 14 of a sturdymaterial, such as compressed paper fibers. The material that makes upthe core layer may be ½ to 1 inch thick or more and is shaped in theform of a tube. A continuous sheet of stock 24 is wound around the core14. The stock 24 may be any type of material. An RFID inlet 26 ispositioned on the core 14. The RFID inlet 26 typically comprises a tag32 in the form of a thin substrate having an antenna 36 positioned onthe substrate, and a radio frequency integrated circuit (“RFIC”) 34. TheRFIC 34 and antenna 36 are electrically coupled to one another, eitherby direct contact or by capacitive coupling. The RFIC 34 may includesemiconductor circuits having logic, memory, and RF circuitry, and maybe a silicon-based chip, a polymer-based chip, or other chips that areknown today or will be developed in the future.

An antenna 36 is positioned on the inlet 26 in electrical communicationwith the RFIC. In a preferred embodiment, the antenna 36 is positionedon the tag 32 of the inlet 26. The tag 32 may be a paper or polymericmaterial, such as polyester, among other known materials. A pressuresensitive adhesive 38, or other attachment medium, may be positioned onone side of the tag 32 for use in attaching the inlet 26 to the surfaceof the core 14. Alternatively, the inlet 26 may be applied using glues,hot melts, water activated adhesives, or other adhering mediums. Theinlet 26 may be applied to the core 14 with an automatic applicationdevice, such as a label applicator, which applies the inlet 26 to theouter surface of the core 14 after it has been formed into a tube.Alternatively, the inlet 26 may be applied after the paper stock 24 hasbeen wound around the core 14. Furthermore, the inlet 26 may be appliedby hand or with an automated process. A preferred position for the inlet26 on the core 14 is near the center of the core, although the inlet 26may be positioned at any location along the length of the core 14.

The antenna 36 on the tag substrate 32 may be an inductive or acapacitive antenna 36 depending on the RF frequency chosen for theapplication. The RFID transponder 26 may be an inductive or a capacitivesystem. One type of capacitive antenna is shown in FIGS. 1, 3, and 4.The capacitive antenna includes two pads 40 of conductive material witha non-conductive gap positioned between the pads 40. An RFIC 34 ispositioned in the gap in electrical contact with both pads 40 of theantenna. The RFIC 34 has terminals (not shown) which may directlycontact the pads 40 or may be otherwise connected to the pads 40 withseparate connectors. The RFIC 34 may alternatively be capacitivelycoupled to the antenna pads 40.

An inductive antenna in the form of a loop 42 with two ends is shownpositioned on a tag 32 in FIG. 2. The RFIC 34 is in electrical contactwith the ends of the loop 42. One end of the loop is electricallycoupled to one of the terminals of the RFIC 34 while the other end ofthe loop utilizes a bridging connector to couple to the other terminalof the RFIC 34.

The inlet 26 may be positioned on an inner surface 44 of the core 14, asshown in FIG. 4, or on an outer surface 46 of the core 14, as shown inFIGS. 1–3. The inlet 26 may also be embedded within the material of thecore (not shown). When the inlet 26 is positioned on the outer surface46 of the core 14, it is positioned on the core 14 prior to theapplication of the stock 24 to the core 14. Alternatively, when theinlet 26 is positioned on the internal surface 44 of the core 14, it maybe positioned on the core 14 either before or after the paper stock 24is wound around the core 14. In FIGS. 3 and 4, the adhesive layer on thetag is shown attached to one side of the tag while the antenna and RFICare positioned on the other side of the tag. Alternatively, theadhesive, antenna, and RFIC may all be positioned on the same side ofthe tag. With this latter embodiment, the tag 32 is the outer mostsurface of the inlet 26 once the adhesive 38 is applied to the surfaceof the core 14, providing a degree of protection for the antenna andRFIC.

It should be noted that RFIC 34 and antenna 36 combinations other thanthose discussed above or shown in the figures may be utilized with theinvention. For instance, the RFIC 34 may be positioned on a tag 32 forease in attachment to a surface of the core 14, or may be directlyapplied to a surface of the core 14 or embedded in the core without atag 32. Furthermore, while the antenna 36 is generally positioned on theinlet 26, the antenna 36 may be positioned on the surface of the core 14instead of on the inlet 26. When the antenna 36 is positioned directlyon the core surface, the RFIC 34, which is electrically coupled to theantenna 36, is positioned on a tag 32 or may be independent of a tag 32.The antenna 36 is positioned on the surface of the core 14 utilizing anyknown technique, such as printing a conductive ink, sputter coating aconductive material, etching, and hot foil stamping, among other knownantenna depositing techniques. Furthermore, RFIC 34 may be coupled tothe antenna 36 by leads, connectors, interposers, or other knowntechniques for coupling an RFIC 34 to an antenna 36.

While the invention has been discussed in the context of rolls of paper,the invention is not limited specifically to paper. Other types ofmaterials may also be wound around the core 14. Moreover, as discussedbelow, the system of the invention may be utilized with any type ofinventory that is transportable by a fork lift truck 18 or similarmaterial handling device. For example, the inventory may include aplurality of cardboard boxes that are filled with a product. An inlet 26may be positioned on an inner or outer surface of each of the cardboardboxes, positioned on the products themselves, or simply positionedinside the box on a floating inlet.

Material handling devices, such as fork lift trucks 18, are typicallyused in a warehouse 12 to move inventory 16, which is often stored onpallets. Fork lift trucks 18 include attachments in the form of arms 22for engaging and moving the pallets, as shown in FIG. 11. The arms 22may also engage the inventory itself without the need for pallets,depending on the size and shape of the inventory.

One type of fork lift truck 18 is known as a clamp truck. Clamp trucks,such as those shown in FIGS. 5–10, are used to lift heavy rolls ofpaper. Clamp trucks include large curved arms 22 a having clamp pads 22b. The clamp arms wrap around the paper roll 10, lift and transport thepaper roll 10, and deposit the roll in either a storage location withinthe warehouse 12, or on a truck or train for transportation out of thewarehouse 12. Since rolls of paper can be costly, it is desirable toelectronically track the location of rolls in a warehouse 12.

The present invention tracks the location of rolls of paper bypositioning an RFID inlet 26 (i.e., RFID transponder) on the core 14 ofeach paper roll 10 and installing a reader 20 on the fork lift truck 18for communication with the RFIC positioned on the RFID inlet 26. Awarehouse position locating system 28 tracks the location of each forklift truck 18 in the warehouse 12. A first computer processor 58 ispositioned on the fork lift truck 18 and a second computer processor 30is positioned in the warehouse 12. Based on the location of the truck inthe warehouse, the position of the paper roll 10 is calculated and theposition and the paper roll's associated unique ID(s) is communicatedfrom the RFID reader 20 to the second computer processor 30. The secondcomputer processor 30 includes a data processor and the data processormaintains the position information and corresponding unique ID for eachitem of inventory 16. The second computer 30 may link this informationto another site, such as the internet, for offsite monitoring. Thesystem permits automatic, at a distance, non-line of sightcommunication.

Referring to FIGS. 5–12, the system of the present design utilizes afork lift truck 18 as a mobile carrier for an RFID reader 20. The reader20 is in communication with the second computer processor 30 in thewarehouse 12 and the first computer processor 58 that is positionedonboard the fork lift truck 18. The reader 20 is electrically ormagnetically coupled to the RFID inlet. The system also utilizes aposition locating system 28, which is in communication with the secondcomputer processor 30 and the first computer processor 58. The secondcomputer processor 30 includes a database system for storing of data.The position locating system 28 operates on principles similar to thatof the global positioning system (“GPS”) and tracks the location ofitems of inventory 16 in the warehouse 12. One type of position locatingsystem 28 is a positional beam system, which utilizes RFID transmitters48 and RFID receivers 50 positioned on each fork lift truck 18, as shownin FIGS. 5, 10, and 11. In a preferred embodiment, the RF polling systemis a receiver 50 having a spinning or stationary flat planar antenna(e)54 positioned on top of each fork lift truck 18 and the transmitters areRFID beacons 48 positioned on the ceiling 52 of the warehouse 12. Theposition locating system 28 may also utilize a truck mounted inertialmeasurement unit 56 (“IMU”), in combination with distance sensors, oranother location measurement device or sensor, which is used to trackthe location of the truck based upon the truck's movement. The positionlocating system is comprised of several sub-systems. One subsystem isthe Radio Frequency Direction Finding system (“RFDFS”), depicted inFIGS. 10 and 11. The RFDFS includes a plurality of RFID transmitters orbeacons and at least one receiver,

In one embodiment, the system processes a number of signals received bythe receivers 50 from the beacons 48 and measures angular positiondifference information for a selected number of signals. In a preferredembodiment, the beacon signals are received by each receiver 50, and twoof the signals are selected, digitized, and processed by the firstonboard computer processor 58. Triangulation and filtering algorithmsare stored in the onboard first computer processor 58, as well astracking algorithms that are utilized to process RFDFS/LocationMeasurement Device measurements. The algorithms are applied to thesignal data in the onboard computer processor 58 to calculate a positionof the lift truck 18 in the warehouse 12 and a position of the item ofinventory 16. The programming in the first computer processor may alsobe utilized to calculate a position of a defined reference point in thewarehouse.

In operation, the reader 20 communicates with the RFIC 34 in aconventional manner. For example, with a passive RFIC 34, the reader 20powers the RFIC 34 so that the RFIC 34 communicates information storedin the RFIC 34 to the reader 20. The reader 20 then communicates theinformation stored in the RFIC 34 to the second computer processor 30.Material identification, manufacture date, customer, and other data arepreferably stored in the RFIC. The RFIC 34 may be written to by thereader 20 to store additional information in the RFIC 34, such asmaterial weight. For example, if the paper roll 10 is moved from a firstposition in the warehouse to a conveyance, information regarding theshipping information may be written to the RFIC. The information mayeither be written over existing information, or added to existinginformation stored in the RFIC 34. Information is also updated in thesecond computer 30 whenever inventory 16 is moved in the warehouse, orremoved from the warehouse.

Each reader 20 is preferably associated with a reader antenna 60. In oneembodiment, shown in FIG. 5, readers 20 are positioned on the arms 22 aof the fork lift truck 18 and a reader antenna 60 is associated witheach of the readers 20. The reader antenna 60 is formed by coating eachfork lift arm 22 a with a conductive material, such as a conductive ink,and coupling the fork lift arms 22 a to the reader 20 by an electricalconnector (not shown). A reader 20 is coupled to each arm so that theleft arm represents an electrical potential that is separate from thatof the right arm. When the fork lift arms 22 a come into contact withthe paper roll, the charge is dissipated through the RFID transpondervia the capacitive couple to allow communication between the readers 20and the RFIC 34 that comes into proximity with the reader 20.

In another embodiment of the system, as shown in FIGS. 6–9, a readerantenna 60 is positioned in a conductive loop 62 that extends outwardlyfrom the fork lift truck 18 and the reader 20 is positioned on the forklift truck 18. The reader antenna 60 is electrically coupled to thereader 20 by cables or other connectors. The reader antenna may includea rigid, conductive tube positioned in the shape of a loop 62 withseveral conductor turns. The loop may include stabilizing members 70that bisect the loop so that the loop forms a ladder-like configuration,as shown in FIG. 6. The reader antennae 60 may be positioned adjacenteach other to form a grid that extends from or is positioned on the forklift truck 18.

In other embodiments, the reader antenna 60 forms a loop shape withoutthe need for stabilizing members, as shown in FIGS. 7–9. The tubes ofthe antenna are preferably formed of a conductive material such ascopper or aluminum. A wire transformer is suspended inside the tube andis buffered from the tube walls by a buffering material, such as aninsulating dielectric. The wire transformer is in electricalcommunication with the reader 20 and is preferably connected to thereader by a cable or other connector. The conductive tube of the loopantenna 62 is utilized to protect the antenna's wire transformer and isalso used to shield the transformer from electromagnetic noise. Theconductive tubes help to shield any electromagnetic noise and drainelectromagnetic current to neutral. Other types of antennaconfigurations and shielding may also be utilized. The antenna ispreferably positioned so it does not interfere with the operation of thearms 22, 22 a or pads 22 b.

FIGS. 6–9 show a variety of locations for the readers 20 and the readerantennae 60. FIG. 6 shows two ladder-like antenna loops, with one of theloops positioned on one side of the lift mast 64 and the otherpositioned on the other side of the lift mast 64. The loops are attachedto the fork lift truck 18 by the back plate 66 with a bracket 68. Theback plate 66 is the portion of the fork lift truck 18 where theattachments, such as the clamp arms 22 a, are connected. The loops 62are angled relative to the lift mast 64 in order to approach or obtain360° RF coverage when an item of inventory is positioned in the arms 22a. The loops are fixed to the back plate 66 by the brackets 68 and donot move when the clamp arms 22 a move. In an alternative embodiment,the reader antenna loops 62 move up and down with the movement of thearms 22 a. The antenna loops are configured to not interfere with themovement of the clamp arms or the movement of the truck into tightspaces. In this regard, it is desirable that the loops do not extendoutside the width of the truck 18. Each reader antenna loop 62 ispositioned on the back plate 66 and coupled to the reader 20 by a cable.The reader 20 may range in size depending on the manufacturer, with atypical size being approximately 6″×4″×2″. A separate reader 20 isgenerally provided for each reader antenna loop 62, although a singlereader may be used with multiplexed antennae. The reader is powered bythe fork lift truck's electrical system, although a separate powersystem may alternatively be provided, if so desired.

FIG. 7 shows two reader loop antennae 62, positioned on either side ofthe lift mast 64. The loops are attached to the lift mast 64 by brackets68, are not movable, and preferably extend the full height of the liftmast 64. Readers 20 are coupled to the loops 62 and are positioned onthe lift mast 64. The readers 20 are electrically coupled to the antennaloops 62 by cables or other connectors. The antenna loops of FIG. 7 aresimilar to the antenna loops of FIG. 6, but do not include thestabilizing members 70. The tubes that form the outer shell of thereader antenna loops 62 are preferably of a size that permits them to bestable and sturdy without the need for stabilizing members 70. Forinstance, 1″ or 2″ copper tubing may be utilized to form the tube loops.As with the embodiment of FIG. 6, the loops are fixed in position by thebrackets 68 and are preferably angled within the roll constant surfaceplane of the clamp arms 22 a and pads 22 b to provide 360° RF readcoverage. The loops 62 are preferably spaced from the lift mast 64 by adistance in order to prevent RF field loss between the lift mast 64 andthe antenna loops 62. A preferred spacing 2″ to 4″.

FIG. 8 shows a reader single loop antenna 62 that is positioned aroundand outlines the lift mast 64. The loop 62 includes tubes and atransformer similar to that discussed above, but is wider than priorembodiments due to the size of the lift mast 64. The reader antenna 60is preferably spaced from the lift mast 64 by 2″ to 4″ in order to avoidany RF field loss between the mast 64 and the antenna 60 and isconnected to the mast 64 by brackets 68 or other connectors. Dependingon the shape and size of the mast, the antenna loop 62 may wrap aroundthe back of the mast 64, as shown in FIG. 8, or may extend over the topand under the bottom of the mast 64. Because of the larger width of theantenna 62 caused by the width of the lift mast 64, effective readranges are obtained. In this embodiment, the reader 20 is positioned ontop of the lift mast 64, although it could be positioned at otherlocations, such as on the antenna loop 62 or the truck body, among otherlocations.

FIG. 9 shows an alternative embodiment where the reader antenna loops 62are recessed into the face 72 of the clamp arms 22 a and clamp pads 22b. Two antenna loops 62 are shown, one positioned on each clamp arm 22a. The loops 62 are tubes that are positioned in troughs on the clamparms 22 a and clamp pads 22 b, and the readers 20 are positioned ontheir respective clamp arms 22 a. In this embodiment, the loops arerecessed below the face 72 of the clamp arms 22 a/clamp pads 22 b inorder to avoid any physical interference between the antenna loops andthe inventory being transported. The antenna loops 62 are suspended inan insulating dielectric positioned between the antenna loop and themetal trough. The insulating dielectric prevents the antenna loop frommaking contact with the metal of the clamp arm 22 a/clamp pad 22 b inorder to avoid any electromagnetic interference or shorting out of theantenna.

In yet another embodiment, the reader antenna loop 62 encompasses theback plate 66. This embodiment is similar to that of FIG. 7, except FIG.7 shows the loop around the lift mast 64. A clearance of 2″ to 4″ aroundthe back plate 66 is preferred in order to avoid any RF field loss. Inthis embodiment, the reader 20 may be positioned on the back plate 66,the arms 22 a, 22 b the lift mast 64, or the truck body.

The reader antenna loops 62 range in size depending on the size of thefork lift truck 18 and the arms 22, 22 a, 22 b. In one embodiment, suchas those where the loops are positioned on either side of the lift mast64, the width of the loop ranges from about 12″ to about 24″, with apreferred width being 20″. In embodiments where the reader antenna 60 ispositioned around the lift mast 64 or back plate 66, the antenna may bewider, such as about 36″. The height of the antenna loop 62 is dependenton the range of coverage desired. For instance, if the lift mast 64 hasa lift height of 48″, the antenna also preferably has a read height of48″ or more. The antenna 60 will typically provide a read coverage forthe entire height of the antenna. Therefore, if a read height of 50″ isdesired, the antenna should be at least 50″ high.

The height and width of the antenna 60 determines the coverage area forreading the RFID inlets 26 positioned on inventory 16. Where numerousitems of inventory 16 are positioned in or on the arms of the fork lifttruck 18 at one time, such as where a pallet carries boxes of products,the reader 20 will read the RFIC 34 of each item of inventory 16. Thus,the computer will know that the particular item of inventory is on thepallet, but will not be able to determine the precise location of theinventory on the pallet. An alternative antenna/reader configuration maybe utilized similar to that shown in FIG. 6, but incorporating aseparate antenna loop and reader for each part of the ladder. With theconfiguration shown in FIG. 6, three separate antenna loops 62 arestacked on top of each other on each side of the lift mast 64 and atotal of six readers 20 are positioned on the fork lift truck 18. Thereaders 20 may be positioned on the clamp arms 22 a, the back plate 66,the lift mast 64, the body of the truck, or the antenna loop 62. Withthis multiple antenna/reader configuration, the reader 20 can be used todetermine the location of the RFIC 34 with greater precision than wherea larger, single loop is utilized. The first computer processor 58 onthe truck 18 utilizes algorithms to more precisely determine theposition of the RFIC 34 by cycling the readers 20 and using field ofstrength measurements, among other methods.

The reader 20 on the fork lift arms 22, 22 a can be Motorola's BiStatix,Philips' Icode, or any other reader that meets the electricalrequirements of the system. Since the paper on the roll creates lossesin the radio frequency signal from the reader 20 and RFIC 34, a lowerfrequency signal may be required to avoid excessive attenuation losses.Advantageously, when the fork lift truck arms or pads are touching thepaper roll 10, the conductive surface of the reader 20 does not havehigh frequency reflections at the paper interface, which helps to reducereflected energy losses.

The fork lift reader 20 may be activated automatically or manually. Forexample, the reader 20 may be manually activated by the fork liftoperator by activating a switch when desired to obtain a reading fromthe RFIC 34 or to write to the RFIC 34. The switch may be positioned inthe cab of the fork lift truck 18 and may be engaged by the operatorwhen the clamp arms 22 a are in close proximity to an item of inventory16. The inventory 16 may be in the grasp of the clamp arms 22 a or pads22 b, or may be positioned near the clamp arms 22 a or clamp pads 22 b.In order for the reader 20 to properly interrogate the RFIC 34, it mustbe close enough to the inventory 16 to obtain a reading. The necessaryproximity requirement is driven by the size and type of antenna 36 thatis coupled to the RFIC 34 installed on the core 14, the size and type ofantenna 60 coupled to the reader 20 on the fork lift arms 22, 22 a, thedistance and type of material through which the reader 20 and RFIC 34signal must travel, the location of the reader 20 relative to the RFIC34, and the existence of any obstructions between the reader 20 and theRFIC 34, among other factors.

The reader 20 may alternatively be automatically activated. For example,the reader 20 may be activated when the clamp arms 22 a or pads 22 bcome in contact with the paper roll 10. A pressure switch may bepositioned on the clamp arms or pads and activated when the clamp arms22 a have contacted a roll of paper 10. In another embodiment, switchesor sensors are positioned on the clamp arms 22 a and activate when theclamp arms 22 a or pads 22 b are brought to a point towards one anotherthat signals the clamp arms have engaged a roll of paper 10.

In a preferred embodiment, pressure switches are associated with themovement of the clamp arms 22 a. The clamp arms 22 a typically includehydraulics that move the arms inwardly and outwardly to grasp a roll ofpaper 10, transport it, and deposit it. In order to grasp a roll ofpaper 10 and transport it, the clamp arms 22 a apply pressure to theroll. Pressure switches are coupled to the movement of the clamp arms 22a in a conventional manner and are sensitive to the pressure beingapplied by the clamp arms 22 a or clamp pads 22 b as they grasp a rollof paper 10. When the pressure reaches a predetermined triggering level,the first processor detects and directs the reader 20 to activate andcommunicate with the RFIC 34. When the clamp arms 22 a and clamp pads 22b release the transported roll of paper 10, the pressure level of theclamp arms 22 a passes by the triggering level and, once again, thereader 20 communicates with the RFIC 34 and first computer processor 58.In operation, the reader 20 interrogates the RFIC 34 and reads the datastored in the RFIC 34. When the fork lift arms 22 a are lowered oropened to release the paper roll 10, the location of the paper roll 10is determined using the position locating system 28. The positioninformation is transmitted from the first computer processor 58 to thesecond computer processor 30 for later use. Each time the paper roll 10is moved, the position information is preferably updated in the secondcomputer processor 30. The position information may be stored even whenthe paper rolls 10 are loaded into trucks and railway cars fortransportation to customers. The position locating system 28 can surveythe frontier of the warehouse to determine when a fork lift truck 18 hasleft the frontier, such as when a truck 18 leaves the warehouse todeposit a roll of paper in a train or truck for transport to thecustomer. In addition, automatic input into the second computerprocessor 30 occurs when an item of inventory is removed from thewarehouse.

In a preferred embodiment, the position locating system 28 is activatedautomatically to determine the position of the receivers 50 on the forklift trucks 18 at appropriate operation periods, such as when the truck18 is positioning an item of inventory 16 in the warehouse 12. In apreferred embodiment, the RFID receivers 50 are continuously receivingthe RFID beacon signals to continually determine the position of theRFID receivers, although other embodiments may use a periodic, ratherthan a continuous sampling.

The number of RFID beacons 48 needed for the warehouse position locatingsystem 28 will depend upon warehouse size, density of paper rolls,operating frequency, and the number of electromagnetic scatteringobjects. FIG. 10 shows a warehouse 12 having multiple beacons 48. FIG.11 shows a warehouse having four beacons 48. The RFID beacon density maybe uniform or non-uniform.

The beacons 48 are transmitters that transmit RF signals at a specificfrequency, where each beacon transmits a different frequency, such as isknown with Frequency Division Multiple Access (“FDMA”) Systems. Eachfrequency is tied to a specific beacon and the receivers can determinewhich beacon they are receiving signals from based upon the frequency ofthe signal they receive. Additionally, the second computer's databasemaps out the location of each beacon. Through triangulation techniques,the receiver location is determined by calculating the angular locationof the sensed beacon in relation to the same beacon's absolute location.In a large warehouse, frequencies may be duplicated when transmittersare spaced so far apart that confusion of location is not likely. Thebeacons 48 are fixed at specific locations so that when an RF signal isreceived by the receiver 50, the location of the signal can be preciselydetermined. The spacing of the beacons 48 is determined using knownspacing techniques.

The receiver 50 is preferably mounted on the fork lift truck 18 andincludes a spinning and/or flat stationary planar antenna(e) for use incontinually communicating with the RFID beacons 48. The receiver 50communicates with all beacons 48 in its relative vicinity and, utilizingtracking algorithms stored in the first computer processor 58, selectsseveral of the signals for processing. The tracking algorithmspreferably select the beacons 48 proactively, by seeking out new beacons48 as the receiver 50 is moved about the warehouse 12. The proactivenature of the tracking algorithm adds to the stability of the system,since the receiver is continually receiving angular measurements fromseveral beacons 48 at a time. The receiver 50 has numerous modules(hardware), some of which include programming for receiving highfrequency signals and down converting them to lower frequencies. Othermodules include programming for digitizing the signals for use with thealgorithms in the first computer processor 58. The modules are storedwithin the first computer processor housing 58 and spinner assemblyhousing 54.

A warehouse environment is potentially susceptible to multipath errorsdue to metal or other structures in the warehouse 12 that reflect theelectromagnetic waves emitted by the RFID beacons 48. Multipath errorsare caused when a radio signal is received directly by an antenna, butthen the same signal is received again as it is reflected off aninterfering structure. The use of “Preprocessing” filters minimizes theinstability effects that multipath may cause by selectively ignoringbeacon multipath measurements. Preprocessing filters can be used onradio signals to filter out any erroneous signals. The signals may thenbe further refined in a Kalman Filter, which is a known multiple-inputsoftware filter that can optimally select or reject, in real time, thesensor inputs based on the quality of the respective sensormeasurements. The Kalman filter may reject erroneous sensor inputs tocalculate the desired output of the position locating system 28 with thelocation measurement unit 56, and a Kalman filter provides improvedoverall navigation accuracy. The Kalman filter may reside in thereceiver 50, in the first computer processor 58, or in the secondcomputer processor 30. A preferred location for the Kalman Filter is inthe first computer processor 58.

In one embodiment of the system, a location measurement device 56, suchas an inertial measurement unit (“IMU”), is positioned on the fork lifttruck 18 and used to track the location of the truck 18 in RF “blind”areas. Inertial measurement units 56 are self-contained positionmeasurement devices that monitor position based upon the movement of thevehicle. Distance sensors are preferably coupled to the inertialmeasurement unit to monitor movement of the truck 18. IMU's may includesuch features as a lateral accelerometer, a longitudinal accelerometer,a yaw rate gyro, and other devices for determining distance traveled andaccurate stop state, among other components. The inertial measurementunit 56 can also be utilized to measure the fork lift trucks headingangle through the use of an electronic compass compared to that of areference (i.e., true North) for use in calculating the position of thetruck. The unit 56 makes calculations of the position of the receiver 50based upon the movement of the vehicle and maintains a stablecalculation up to about 12 seconds. It works in concert with the RFDFS28, which updates the “absolute” position of the receiver 50 based uponmeasurements taken from the beacons 48 through the receiver 50. Theinertial measurement unit 56 and distance sensors update the Kalmanfilter during time periods between Kalman filter updates by the RFDFS28. In this way, the Kalman filter output is stable during movements andthe system continually has position information.

Other types of devices and/or sensors, or combinations of sensors anddevices, may also be used as the location measurement unit 57 instead ofthe IMU. For example, position information can be determined by usingdistance sensors, which are typically coupled to the wheels of the truckand are used to determine distance traveled based upon rotation of thewheels, in combination with an electric compass, which is used toestablish heading. A combination of these two devices are used todetermine the position of the truck between updates from the positionlocating system. Other devices, besides those described above, may alsobe utilized to determine the position of the truck between updates. Theterm “location measurement device” is used herein to describe either atypical inertial measurement unit or other types of devices. The purposeof the location measurement device is to determine the location of thetruck between communications with the position locating system.

Referring to FIGS. 10 and 11, the position of the receiver 50 in thewarehouse 12 is determined through triangulation calculations of knownRFID beacon locations in the warehouse 12. Algorithms utilized toperform the position calculations are stored in the first onboardprocessor 58. The second computer processor 30 is generally utilized forstoring inventory data and for handling communications to the lift truck18 drivers. In order to avoid overloading the second computer processor30 with the numerous calculations necessary to determine the position ofthe receiver 50, these calculations are preferably performed on thefirst onboard computer processor 58. The necessary algorithms fordetermining the position of the lift truck 18 in the warehouse 12 arepreferably stored in the first computer processor 58. These algorithms,for example, take the signals received from all the beacons 48 inrelative proximity to the truck 18 and perform a triangulationcalculation to determine the position. In a preferred embodiment, two ofthe beacons 48 are utilized to perform the triangulation calculation.Therefore, two signals are selected from the numerous signals receivedby the first onboard processor 58. The triangulation technique measuresthe angular position of the spinner when the known beacon position isread.

The first onboard computer processor 58 is utilized to resolve errorsfrom the calculations to improve the accuracy of the calculated positioninformation. Algorithms are utilized to resolve errors that are inherentin the system such as multipath, partial blockage, or other errors, asknown by those of skill in the art. As previously discussed, onealgorithm that may be used to correct for any erroneous measurements inthe position calculation is a Kalman Filter. The first computerprocessor 58 also includes algorithms for use in calculating theposition of the item of inventory 16 based upon the calculated positionof the lift truck 18.

When the item of inventory 16 is a paper roll 10, the algorithms storedin the first computer processor use an x-y offset to determine where thecenter of the core 14 is based on the size of the paper roll and theorientation of the truck 18. An algorithm may also be utilized todetermine the height at which the paper roll is positioned to accountfor stacking of the paper rolls 10. In this regard, the fork lift truck18 preferably includes a device for determining the deposit height ofthe roll. In a preferred embodiment, the core center location is theposition information transmitted to the RFIC 34 and second computerprocessor 30.

In operation, the receiver 50 on the fork lift truck 18 first runs aninitial sweep of all the beacons 48 in the immediate vicinity of thetruck 18 to determine an initial position of the truck 18. Paper rollposition information is also transmitted to the second computerprocessor 30 whenever inventory is moved. The position locating system28 stores the position of each roll, with an accuracy of approximately±1 foot. The second computer processor 30 can provide an immediatewarning when inventory is improperly positioned in the warehouse 12, andcan proactively suggest the proper material placement position. Inaddition, the second computer processor 30 can provide independentverification of shipment contents, interface with all warehouse trackingsystem software packages, provide inventory reports if so desired, andmay be linked to the internet.

In addition to positioning readers 20 on the clamp trucks 18, the systemmay be expanded to also include readers positioned at other placeswithin the manufacturing and transportation system, such as on papermachine rewinders and process points, as well as on trucks or traincars, the invention not being limited to placement of readers 20 on forklift trucks 18 alone. In addition, the receivers 50 may be positioned asstationary receivers at points within the warehouse 12 to provide a typeof Differential GPS system, as known by those of skill in the art.

In an alternative embodiment of the system, the fork lift truck 18includes the beacon transmitter 48 and receivers 50 are positionedthroughout the warehouse 12. In either case, the captured positionaldata will be processed by the first computer processor 58 and the uniqueinformation on the RFIC 34 on each item of inventory 16 will be sent tothe second computer processor 30 for processing and distribution.

The position locating system 28 has been discussed herein in the contextof a pseudo-GPS type system. Those of skill in the art will recognizethat variations and improvements may be incorporated in the presentdisclosure to improve the operation of the system, according tocurrently existing knowledge in the art. The brief description of theposition locating system discussed herein illustrates several of manypossible embodiments. Furthermore, the invention is not limited to theparticular position locating system described herein. Other types ofposition locating systems may also be utilized, including those that arenot based upon GPS principles.

For example, in yet another embodiment of the system, the RFDFS system(including the beacons and receivers) may be entirely replaced by aposition locating system that includes RFIC's and their associatedantennae installed in or on the floor 74 of the warehouse 12. The RFIC'sare preferably passive and are powered by an external reader. As shownin FIG. 12, a plurality of RFID inlets 26 are installed in the floor 74of the warehouse 12 in a regular grid pattern. The position of each RFICon each inlet 26 within the grid is known since the inlets 26 are fixedpositionally on the floor 74. The inlets 26 may be positioned on top ofthe floor 74, or, in a preferred embodiment, are embedded in the floor74 and covered by a protective material, such as a laminate.

The RFID inlets 26 replace the beacons 48 discussed above in connectionwith FIGS. 10 and 11. A reader or readers positioned on the truck 18replace the receivers 50. In one embodiment of the alternative system, asingle additional reader 76 is installed on the truck 18 and ispositioned for communicating with the RFIC's installed in the floor 74.The reader has an antenna 60 and the inlet 26 have antennae 36. Thereader antenna 60 and inlet antennae 36 are configured to provide alimited read distance such that dead bands 78 are found on the floor 74.In the dead bands, the reader 76 loses communication with the inlets 26.

The dead bands 78 are utilized to avoid readings from two inlets 26 at asingle time. The dead bands 78 are configured such that only one RFIDinlet 26 is readable at a single time by the reader 76. During times inwhich the reader 76 is positioned in a dead band 78, the IMU 56, orlocation measurement unit, may be utilized to supplement positioninformation, as discussed above. Position information can be calculatedby the onboard computer 58 and transmitted to the base station computerprocessor 30 via wireless means.

In another embodiment of this alternative system, two or more additionalreaders 76, 80 are positioned on the forklift truck 18 at spacedlocations from each other. For instance, one reader 76 is positioned atthe front of the truck 18 and the other 80 is positioned at the rear ofthe truck 18. The multiple readers can be used together to triangulate aposition of the truck 18. When one of the readers is in a dead band 78,the other reader 80, which is preferably not positioned in a dead band78, can continue to determine the position of the truck 18 until theother reader 76 reestablishes contact with an inlet 26. With multiplereaders 76, 80, the readers can actually replace the IMU 56 and itsassociated sensors so that the position of the truck 18 can bedetermined in a less mechanically complicated manner. Alternatively,instead of using multiple readers 76, 80, a single reader could beutilized that has multiple antennae positioned around the truck body.The reader can multiplex through the multiple antennae to obtainreadings from nearby inlets 26. The multiple readings can be used totriangulate a position of the truck 18. Two or more antennae can bepositioned around the truck. Since readings can be performed in acontinuous manner, the IMU can be eliminated.

Readings performed by the readers 76, 80 are preferably continuous, butmay be intermittent. In addition, the inlets 26 may alternatively bepowered to provide a longer read range, if desired. Dead bands 78 may besized so that they are smaller in width and length than a typical forklift truck 18 in order to minimize the likelihood that two or more ofthe antennae will be positioned in a dead band 78 at a single time.

The systems described above provide a number of benefits in real time,including the ability to track the location of inventory, improvewarehouse utilization by mapping the warehouse, improve the placement ofinventory utilizing an alarm system, provide independent shipmentverification, and provide an electronic physical inventory.

A reader and reader antenna similar to that depicted in FIG. 6 weretested and achieved full read/write capability through a base stock rollof paper that was 75 inches thick. In addition, full mast height readcoverage was attained with the antenna design so that the reader 20could read all stacked rows of paper.

In the preferred embodiments discussed herein, the RFIC 34 is passive.However, a semi-passive or active system is also contemplated for usewith the present design. If a semi-passive or active RFIC is utilized, abattery is coupled to the RFIC. In addition, a sensor may beelectrically coupled to the RFIC for communication with the RFIC, suchas a MEMS (micro electromechanical system) sensor. The sensor may beused to read environmental or other conditions, including physical andchemical properties, in the vicinity of the sensor. Examples ofenvironmental properties include temperature, pressure, and humidity,among other conditions. Multiple sensors may be utilized with a singleor multiple RFICs.

The sensors can transmit a sensed condition to the RFIC when commandedto do so. In this regard, the RFIC may be passive, semi-passive, oractive. When the RFIC is passive, the reader powers the RFIC and theRFIC then takes a reading of the condition with the sensor. The sensedcondition is then transmitted back to the reader. When the RFIC isactive or semi-passive, it is battery powered such that the RFIC and aclock on the RFIC are continually powered. The battery powered RFIC canindependently signal the sensor periodically to sense a condition andthe sensed condition is transmitted to the RFIC for storage in a log orimmediate transmission to a reader. Certain types of sensors alsorequire battery power and the power needed by the sensor may be providedby the same battery that is utilized to power the RFIC.

The sensor can be built directly into the RFIC or connected to the RFICby a connector. Alternatively, the sensor can operate by wireless signaltransfer, so that a physical link between the sensor and RFIC is notrequired. The sensor and battery may be positioned on the substrate ofthe tag, or may be positioned independently of the substrate andelectrically coupled to the RFIC. One type of passive sensor that may beutilized, for example, to read a temperature is manufactured by SCS ofSan Diego, Calif. A type of active sensor that may be utilized, forexample, to record temperature data is manufactured by KSW of Germany.Other types of sensors may also be utilized.

A variety of commercially available tags, inlets, and radio frequencyintegrated circuits are contemplated for use with the claimed invention.For example, tag suppliers include Poly Flex Circuits, CrossTechnologies, and Global ID. RFIC suppliers include PhilipsSemiconductor, Temic, and E. M. The preferred tags are low profile inorder to avoid marking the paper on the roll.

While various features of the claimed invention are presented above, itshould be understood that the features may be used singly or in anycombination thereof. Therefore, the claimed invention is not to belimited to only the specific embodiments depicted herein.

Further, it should be understood that variations and modifications mayoccur to those skilled in the art to which the claimed inventionpertains. The embodiments described herein are examples of the claimedinvention. The disclosure may enable those skilled in the art to makeand use embodiments having alternative elements that likewise correspondto the elements of the invention recited in the claims. The intendedscope of the invention may thus include other embodiments that do notdiffer or that insubstantially differ from the literal language of theclaims. The scope of the present invention is accordingly defined as setforth in the appended claims.

1. A system for reading an RFIC associated with an item of inventory ina warehouse comprising: at least one material handling device having atleast one member for use in transporting an item of inventory, said itemof inventory having an RFIC associated therewith; at least one RFIDreader coupled to the at least one material handling device for readingthe RFIC associated with the item of inventory when the item ofinventory is in proximity to the at least one material handling device;a computer processor in communication with the at least one RFID readerfor receiving information from the RFID reader and transmittinginformation to the RFID reader; a position locating system fordetermining the position of the item of inventory in the warehouse, saidposition locating system for transmitting information to the at leastone RFID reader and the computer processor, the position locating systemcomprising a plurality of RFID transmitters and at least one RFIDreceiver, the at least one RFID receiver is positioned on the at leastone material handling device and the plurality of RFID transmitters arepositioned at spaced locations throughout the warehouse, the computerprocessor includes programming for receiving and processing the signalstransmitted by the plurality of RFID transmitters and received by the atleast one RFID receiver and the programming is for calculating aposition of the at least one RFID receiver on the at least one materialhandling device in the warehouse, the computer processor furtherincludes a first computer processor positioned on the at least onematerial handling device and a second computer processor positioned inthe warehouse, with the first computer processor including theprogramming for determining the position of the at least one RFIDreceiver on the at least one material handling device within thewarehouse based upon the received and processed signals; and a locationmeasurement device mounted on the at least one material handling devicefor determining the position of the at least one material handlingdevice based upon the movement of the device, the first computerprocessor receives signals from the location measurement device, theposition locating system, the at least one RFID reader, and the RFIC andthe second computer processor includes programming for determining theposition of the item of inventory and includes a database for storage ofthe position of the item of inventory, wherein the location measurementdevice determines the angle of the at least one RFID receiver relativeto each of the plurality of RFID transmitters and the programming in thefirst computer processor is for calculating the position of the at leastone RFID receiver and includes triangulation calculations that are inpart dependent on the angle of the at least one RFID receiver relativeto each of the plurality of RFID transmitters; and further comprisingprogramming for correcting errors in the calculation.